The present invention relates to drilling apparatuses and, more particularly, to an axial feed apparatus having an adjustable feed stop and associated method.
The production of components of an assembly, for example, airplane structural components, often requires that holes be drilled in the components to accommodate the fasteners that secure the assembly together. In some instances, the drilled holes may also need to be countersunk. Typically, the countersink has a preferred depth where the diameter of the countersink is matched to the fastener being used. If the countersink is not deep enough, the fastener may protrude outwardly of the component surface. If the countersink is too deep, particularly in a thin-section component, the hole associated with the countersink may be unacceptably large, the structural strength of the component may be adversely affected, and the fastener may not be able to securely fasten the component. In addition, the excess countersink depth, after the fastener has been installed, will define a cavity which may undesirably collect debris or disrupt airflow about the component. Further, since these components are generally fabricated in a manufacturing operation, where multiple holes must be drilled and countersunk in one or more components, consistency of the countersink depth is also typically required. In some instances, it is also desirable that a drill/countersink operation be performed in a single pass of the drilling/countersinking device in order to reduce the time and additional costs associated with rework or multi-pass procedures.
Drilling and countersinking are related processes which may be accomplished using two or more separate cutters or a single cutter capable of performing both functions. However, the countersinking operation is often the most sensitive to the depth of the cut than the drilling operation. Thus, the term xe2x80x9ccountersinkingxe2x80x9d will be used herein for the sake of simplicity, but it is understood that any description of a countersinking operation is equally applicable to a drilling operation.
In some manufacturing operations, countersinking processes are manually performed using a handheld drill motor. Where the operation includes a countersinking process, a mechanism for controlling the depth of the countersink may be secured in the chuck of the drill motor, to the drill motor, or to the cutter itself. However, a manual countersinking operation may be unacceptable for some manufacturing operations due to inconsistency caused by the operator(s). In addition, the depth control mechanism may require frequent adjustments to maintain a consistent countersink, particularly in the event that, for example, the cutter is changed or adjusted or a different drill motor is used for the process. Thus, there exists a need for a countersinking device capable of operating automatically with minimal operator involvement. In addition, there exists a need for a device capable of consistently, accurately and repeatably controlling the depth of a countersink. Such a device should require minimal adjustments to obtain and/or maintain the desired countersink depth, even if the cutter is changed or a different drill motor is used for the operation.
In some situations, countersinking processes may be performed with, for example, pneumatic power feed equipment, wherein a pneumatic drill motor is used to turn a cutter while an integral feed mechanism feeds and retracts the cutter over a predetermined distance. The relative positioning of the component or workpiece with respect to the travel of the cutter generally determines the depth of the countersink. In practice, the depth of the countersink may be controlled by a mechanism interacting with the chuck, the cutter, and/or the drill motor. However, such a device, much like the manual drill motor previously described, may require frequent adjustments to maintain a consistent countersink, particularly in the event that, for example, the cutter is changed or adjusted or a different drill motor is used for the process. In some instances, adjusting the device may be a complicated procedure requiring at least partial disassembly of the countersinking apparatus.
Alternatively, a dead stop may be used in conjunction with the feed mechanism, wherein the dead stop stops the feed mechanism, and thus the cutter, at a predetermined limit. However, the feed mechanism may not necessarily be aligned with or securely fixed to the drill motor, thereby possibly causing unacceptable deviations from the desired countersink depth since the feed mechanism may not be able to sense and/or respond to the actual forces experienced by the cutter. Further, the feed mechanism may form an integral assembly with the drill motor, thereby limiting the applicability of depth control mechanism if, for example, a different drill motor must be used for the operation due to size or accessibility constraints in the countersinking process. Thus, there exists a further need for a device capable of consistently, accurately and repeatably controlling the depth of a countersink cutter that is driven by a drill motor and fed by pneumatic power feed equipment. Such a device should be in communication with the cutter such that the position of the cutter and/or the forces experienced by the cutter can be included in the determination of the desired countersink depth. The device should also be able to obtain and/or maintain the desired countersink depth if the cutter is changed or a different drill motor is used for the operation and preferably accomplishes this consistency without requiring excessive and/or complicated adjustments.
Thus, there exists a need for pneumatic power feed equipment, particularly equipment used in countersinking processes in a manufacturing operation, having a device capable of consistently, accurately and repeatably controlling the depth of the countersink. Such a device should also be able to obtain and/or maintain the desired countersink depth, even if the cutter is changed or a different drill motor is used for the operation, and preferably accomplishes this consistency without requiring excessive and/or complicated adjustment. The device should also be in communication with the cutter such that the position of the cutter and/or the forces experienced by the cutter can be included in the determination of the desired countersink depth.
The above and other needs are met by the present invention which, in one embodiment, provides an axial feed apparatus having an adjustable feed stop. The apparatus generally comprises a hydraulically-actuated device, a sleeve, a spindle, and a collar. The hydraulically-actuated device comprises a feed member slidably disposed within a housing. The sleeve has a first end engaging the housing and a second end extending outwardly therefrom, wherein the second end defines a series of graduations thereabout. The spindle has a feed stop extending into the housing through the sleeve such that the feed stop is capable of engaging the feed member and providing a feed limit. The collar surrounds the spindle outwardly of the housing and is rotationally fixed with respect to the spindle. The collar further defines a series of graduations thereabout corresponding to, and engageable with, the sleeve graduations. The spindle is thereby prevented from rotating when the collar graduations engage the sleeve graduations. The collar is firther slidably engaged with the spindle to allow disengagement of the graduations and rotation of the spindle. Preferably, the graduations and the spindle are configured such that a rotational change of the collar graduations with respect to the sleeve graduations moves the feed stop by a corresponding axial distance.
In some instances, the hydraulically-actuated device comprises a pneumatic drill motor having a power feed module and, in other instances, a hydraulic power feed module. The apparatus may further comprise a mechanical bias member operably connected between the spindle and the collar in order to bias the collar graduations toward the sleeve graduations, wherein the mechanical bias member may comprise, for instance, a coil spring. In addition, the sleeve and the spindle are threadedly engaged. Accordingly, the graduations and the spindle are configured such that a rotational change of the collar graduations with respect to the sleeve graduations results in an axial movement of the spindle with respect to the sleeve and may correspond to moving the feed stop at a rate of, for example, no more than 0.001 inches/graduation. The apparatus may further comprise a jam nut engaging the spindle and configured to selectively retain the collar graduations in engagement with the sleeve graduations. Where the spindle engages the hydraulically-actuated device, a sealing member may further be provided to form a seal between the spindle and the housing, wherein the sealing member may comprise an o-ring disposed about the orifice and configured to sealingly engage the spindle. Preferably, the spindle is uniaxially disposed with respect to the feed member to provide a positive stop.
Another advantageous aspect of the present invention comprises an axial feed drilling apparatus having an adjustable feed stop. Generally, the apparatus comprises an axial feed device and a drill motor adapted to rotate a cutter. The axial feed device has a feed member adapted to feed the cutter, wherein the feed member is moveable toward a feed stop disposed uniaxially with respect thereto. The axial feed device further has first and second members with respective graduations that are capable of interacting, such that a change in engagement between the interacting first and second graduated members moves the feed stop by a predetermined axial distance. The axial feed device thereby provides an adjustable feed limit where the feed member engages the feed stop. In some instances, the apparatus further comprises a retraction mechanism for retracting the feed member from the feed limit.
In some embodiments, the axial feed device may be hydraulically actuated and may further comprise a housing having a feed member slidably disposed therein, a sleeve, a spindle, and a collar. The sleeve comprises the first graduated member, which has a first end engaging the housing and a second end extending outwardly of the housing, wherein the second end defines a series of graduations thereabout. The spindle threadedly engages the sleeve and has an end comprising the feed stop. The feed stop extends into the housing such that the feed stop is capable of engaging the feed member. The collar comprises the second graduated member and surrounds the spindle outwardly of the housing. In addition, the collar is rotationally fixed with respect to the spindle and defines a series of graduations thereabout corresponding to, and engageable with, the sleeve graduations. In this manner, the spindle is prevented from rotating when the collar graduations engage the sleeve graduations. Preferably, the collar slidably engages the spindle to allow disengagement of the graduations and therefore rotation of the spindle. The graduations and the spindle are configured such that a rotational change of the collar graduations with respect to the sleeve graduations moves the feed stop by a corresponding axial distance. The apparatus may further comprise a jam nut engaging the spindle and configured so as to selectively retain the collar graduations in engagement with the sleeve graduations. Still further, the apparatus may comprise a mechanical bias member such as, for example, a coil spring, operably connected between the spindle and the collar to bias the collar graduations towards the sleeve graduations. Generally, the graduations and the spindle are configured such that a rotational change of the collar graduations with respect to the sleeve graduations corresponds to an axial movement of the feed stop of, for example, no more than 0.001 inches/graduation.
Still a further advantageous aspect of the present invention comprises an axial feed drilling apparatus having an adjustable feed stop. Generally, the apparatus comprises a pneumatic drill motor adapted to rotate a cutter, a power feed module, and a stop device. The power feed module has a moveable feed member adapted to feed the cutter, while the stop device is disposed uniaxially with respect to the feed member and has a feed stop. The stop device also has first and second members with respective graduations that are capable of interacting such that a change in engagement between the interacting first and second graduated members moves the feed stop by a predetermined axial distance, the stop device thereby providing an adjustable feed limit where the feed member engages the feed stop.
The stop device may further comprise a sleeve and a collar. The sleeve comprises the first graduated member and has an end defining a series of graduations thereabout, wherein the sleeve is further configured to threadedly engage the feed stop. A collar comprises the second graduated member and surrounds the feed stop outwardly of the sleeve, wherein the collar is rotational fixed with respect to the feed stop and defines a series of graduations thereabout corresponding to, and engageable with, the sleeve graduations. Accordingly, the feed stop is prevented from rotating when the collar graduations engage the sleeve graduations. The collar is also slidably engaged with the feed stop to allow disengagement of the graduations and rotation of the feed stop, wherein the graduations and the feed stop are configured such that a rotational change of the collar graduations with respect to the sleeve graduations moves the feed stop by a corresponding axial distance.
Still another advantageous aspect of the present invention comprises a method of controlling the axial feed of a drilling apparatus. First, a drill motor is engaged with a feed member of an axial feed device, wherein the drill motor is adapted to rotate a cutter. A feed stop on the axial feed device is then adjusted. The axial feed device generally comprises first and second members with respective graduations that are capable of interacting. Accordingly, adjusting the feed stop further comprises changing the engagement of the graduations of the first and second members to axially move the feed stop by a predetermined amount. The feed member is then moved into engagement with the feed stop to thereby feed the cutter to an adjustable feed limit.
More particularly, adjusting the feed stop further comprises moving one member axially with respect to the other member to disengage the respective graduations, then rotating one member with respect to the other to axially move the feed stop, and then re-engaging the respective graduations to secure the feed stop at a predetermined position. In some instances, adjusting the feed stop further comprises moving one member with respect to the other to provide an axial movement of the feed stop of, for example, no more than 0.001 inches/graduation. According to some embodiments, the method may further comprise locking the feed stop by preventing disengagement of the first and second members following adjusting of the feed stop, wherein locking of the feed stop may comprise biasing one member toward the other with a mechanical biasing device such as, for example, a coil spring.
Thus, the adjustable feed stop implemented in an axial feed apparatus for a drilling device according to embodiments of the present invention is capable of consistently, accurately, and repeatedly controlling the depth of a countersink. In some instances, the axial feed apparatus with the adjustable feed stop is modular and allows different drill motors to be used therewith. In these situations, the drill motor can be relatively easily changed and the new drill motor readily adjusted to maintain consistency with previous countersinks. Such a device is also capable of being easily adjusted when necessary in response to changes in other factors such as, for example, changing of the cutter. Thus, the axial feed device having an adjustable feed stop according to embodiments of the present invention provides a mechanism for obtaining consistent countersinks in a manufacturing operation by providing an automated axial feed system having a readily adjustable feed stop. The feed stop mechanism according to embodiments of the present invention allows the feed stop to be easily and accurately adjusted even if different cutters or drill motors are used. Such a device, though requiring less frequent adjustments, does not require disassembly of the machine in order to adjust the countersink depth by a trial-and-error process. Calibrated graduations are provided which indicate the position of the feed stop and are capable of moving the feed stop by a predetermined axial distance. The adjustable feed stop according to embodiments of the present invention therefore provides a more consistent and positive control for a drilling apparatus having an axial feed device as compared to the prior art.